Generic Data source using FM for BOM Item data is not saving

Hi Experts,

This is the first time I post on this forum.

I am creating a custom datasource (ycp_bom_itm) based on Function Module in R/3 which get data from MAST and STPO.

I have defined the Function Module and the extraction structure as well.

So While saving the Data source i am getting Error as

" Units field MEINS for field ZMENGE of DataSource ycp_bom_itm is hidden

     Message no. R8147"

Does any of you have experience of this issue? Please Help to solve this issue

Thank's In advance